Phycologia (2007) Volume 46 (4), 429–439 Published 5 July 2007 Taxonomic reappraisal of the freshwater brown algae Bodanella, Ectocarpus, Heribaudiella, and Pleurocladia (Phaeophyceae) on the basis of rbcL sequences and morphological characters LINDA A.R. MCCAULEY{ AND JOHN D. WEHR* Louis Calder Center – Biological Field Station and Department of Biological Sciences, Fordham University, Armonk, NY 10504, USA L.A.R. MCCAULEY AND J.D. WEHR. 2007. Taxonomic reappraisal of the freshwater brown algae Bodanella, Ectocarpus, Heribaudiella,andPleurocladia (Phaeophyceae) on the basis of rbcL sequences and morphological characters. Phycologia 46: 429–439. DOI: 10.2116/05-08.1 This study examines the phylogenetic relations among freshwater species of brown algae using RUBISCO large subunit (rbcL) sequences, in conjunction with diagnostic morphological and developmental traits. We focused on the phylogenetic and taxonomic placement of five freshwater species, Bodanella lauterborni, Ectocarpus siliculosus, Heribaudiella fluviatilis, Pleurocladia lacustris,andPorterinema fluviatile, each of which has traditionally been assigned to the Ectocarpales by most authors. These freshwater species were compared with 26 marine taxa of brown algae from nine orders, with particular emphasis on families within the Ectocarpales. Results of BLASTn searches and later phylogenetic analyses placed all freshwater taxa within the Phaeophyceae, but phylogenetic inferences do not support their traditional classifications at the ordinal level. There was no support for the inclusion of H. fluviatilis or B. lauterborni in the Ectocarpales, but instead formed a well-supported clade intermediate between the Syringodermatales and Sphacelariales. Although morphologies of these two species are relatively distinct and remain stable in culture, B. lauterborni nested between two populations of H. fluviatilis (on the basis of rbcL data) from British Columbia and Germany, making a reclassification of these two species necessary. Molecular and morphological data clearly place two other freshwater taxa, Pleurocladia lacustris and (freshwater) E. siliculosus in the Ectocarpales, each nesting among marine members of the Ectocarpaceae. When compared with sequences from 13 species from several families within the Ectocarpales, Pleurocladia is most closely related to members of the Ectocarpaceae and may be a sister taxon to the Scytosiphonaceae. DNA sequences from a freshwater isolate of E. siliculosus from Australia were nearly identical to those from a marine isolate from Germany. Molecular data did not resolve the ordinal status of a freshwater Porterinema fluviatile, but indicated that this species should not be classified within the Ectocarpales. KEY WORDS: Bodanella, Brown algae, Ectocarpales, Ectocarpus, Freshwater, Heribaudiella, Phaeophyceae, Phylogeny, Pleurocladia, rbcL, RUBISCO INTRODUCTION characters to determine the classification of freshwater members of the class. These schemes place most or all The Phaeophyceae is a diverse class of multicellular algae freshwater taxa in the Ectocarpales or Sphacelariales ranging in size from microscopic forms to huge kelps and largely on the basis of their filamentous growth forms occur from arctic to tropical biomes (Bold & Wynne 1978; (Starmach 1977; Bold & Wynne 1978; Bourrelly 1981; Van den Hoek et al. 1995). Members of this class exhibit Pueschel & Stein 1983; Van den Hoek et al. 1995). a wide range of morphologies, reproduction, and ultra- Five freshwater species are most often classified within structure, and comprise roughly 265 genera and between the Ectocarpales sensu lato, although placements within 1500 and 2000 species (Van den Hoek et al. 1995; De families vary a great deal. Pleurocladia lacustris A. Braun Reviers & Rousseau 1999). Of all these species, , 1% (seven (Family: Ectocarpaceae or Chordiariace) was the first species) has been documented to occur in freshwater ‘‘true’’ freshwater brown alga described in the literature environments (Starmach 1977; Bourrelly 1981; Wehr 2003). (Braun 1855). It is a creeping, infrequently branched Although the study of freshwater brown algae has had filament (with one or rarely two parietal chloroplasts) that a long history, with several genera known for . 100 years, occasionally produces upright, centrifugal (arched), multi- ply branched filaments, creating small cushion-like thalli. their classification and phylogeny is unclear. Well-docu- Filaments frequently produce unilocular sporangia (plur- mented populations of several species are few, making ilocular sporangia rarely reported) and hairs (under P- thorough examinations of their morphology, reproduction, limitation; Wehr 2003), and grow on rocks or aquatic and phylogeny difficult (Wehr 2003). To date, studies have plants in lakes and rivers (occasionally endophytic) in relied on morphological, reproductive, and ultrastructural Europe and North America (Waern 1952; Wilce 1966; Bourrelly 1981). The most commonly reported species, * Corresponding author ([email protected]). Heribaudiella fluviatilis (Areschoug) Svedelius (Family un- { Present address: Woods Hole Oceanographic Institution, determined), is a thick-walled, crust-forming alga that Woods Hole Road, Woods Hole, MA 02543. colonizes rocks in streams. Cells have multiple discoid 429 430 Phycologia, Vol. 46 (4), 2007 chloroplasts, and thalli are composed of multiply branched have marine counterparts (species within each genus), prostrate filaments and erect, mostly dichotomously whereas the three other genera do not. branched filaments that bear unilocular or plurilocular Although no classification scheme for the Phaeophyceae sporangia (Starmach 1977; Wehr & Perrone 2003). It has has been fully accepted by all workers, recent syntheses that been reported from several hundred (mostly stream and combine molecular and traditional characters have river) locations worldwide (Wehr & Stein 1985; Wehr 2003). emerged. One such classification characterizes members of Bodanella lauterborni Zimmerman (Family undetermined) the Ectocarpales as simple, uniseriate filamentous forms is a thick-walled, prostrate (creeping) branched filament whose cells have one or few large band-like chloroplasts with multiple chloroplasts, and unknown reproductive and a stalked, pyriform pyrenoid (Rousseau & De Reviers structures (Zimmerman 1928; Bourrelly 1981). It has been 1999). These and other details have not been fully assessed reported to colonize rocks in a few lakes in Europe (Wehr in the freshwater taxa. Grouping of marine taxa is also 2003). Ectocarpus siliculosus (Dillwyn) Lyngbye (Family: strongly supported by molecular studies, which show that Ectocarpaceae) is primarily a marine or brackish species, several taxa traditionally classified within the Ectocarpales, but one freshwater population has been described from Chordariales, Dictyosiphonales, and Scytosiphonales form Australia (West & Kraft 1996) and another inland a strongly supported monophyletic group (Rousseau & De population was reported from a river polluted by potassium Reviers 1999; Draisma et al. 2001; Rousseau et al. 2001). mine wastes (Geissler 1983). This alga exhibits typical De Reviers & Rousseau (1999) also excluded the crust- Ectocarpus morphology with infrequent branching and forming Ralfsia (classified with the Ectocarpales or ribbon-like parietal or spiral chloroplasts (with pyrenoids). Ralfsiales) from the Ectocarpales on the basis of both Plurilocular sporangia have been observed in the Australian molecular data and the absence of characteristic pyrenoids. population, but unilocular sporangia are documented only Tan & Druehl (1994) showed that Ralfsia was more closely in marine populations (West & Kraft 1996). associated with members of the Desmarestiales, Dictyo- Porterinema fluviatile (Porter) Waern is an enigmatic tales, Fucales, Laminariales, Sphacelariales, and Syringo- species that inhabits marine, estuarine, and freshwater dermatales, rather than with members of the Ectocarpales, habitats and is classified in the Ectocarpales by some on the basis of 18S rDNA sequence data. These latter authors (Waern 1952; Bourrelly 1981; Wehr 2003) and in findings with marine taxa are of importance for the present the Ralfsiales by others (Wilce et al. 1970). It is a simple, study, because most freshwater taxa have been classified rarely branched alga with creeping filaments (with 1–3 within the Ectocarpales, and none of the recent classifica- lobed, parietal chloroplasts) that may form loosely ar- tion schemes or molecular approaches has considered the ranged monostromatic discs on plants or rocks, or live freshwater genera or species (Starmach 1977; Bourrelly endophytically in some aquatic plants or other algae 1981; Wehr 2003). (Waern 1952). Plurilocular sporangia are apparently Molecular studies using the 18S rDNA and RUBISCO common and characteristically form four-celled terminal large subunit (rbcL) genes have proven useful for inferring clusters or crowns (Waern 1952; Dop 1979). In general, the phylogenetic relations among orders, families, and genera classification of freshwater taxa, on the basis of at least of marine brown algae (e.g. Assali et al. 1990; Andersen et some morphological features, agrees with the circumscrip- al. 1998; Mu¨ller et al. 1998; Peters & Ramı´rez 2001; tion of the Ectocarpales described by De Reviers & Draisma et al. 2001, 2002; Burrowes et al. 2003) and so Rousseau (1999), with the possible exception of the genus should be considered in efforts to understand the evolu- Heribaudiella,